An Introduction to the Vertebrates Flashcards
(21 cards)
Agnathans
A small group of jawless vertebrates
- not a taxonomic group
- include much extinct or armoured fish (octraderms)
Cyclostomata
living groups include hagfish and lamprey
- look similar
Hagfish
- about 40 species
- feed on invertebrates or are scavengers
- skull but no vertebrae
Lamprey
- about 40 species
- feed on the fluid or blood of fish
- can cause problem to fisheries
- mouth designed for attaching, scraping
Gnathostomes
- all the other vertebrates that have jaws
Advantages of Gnathostome
Different food Resources
Defence
Other uses
Advantages of Gnathostome - Different food Resources
- grip becomes surer
- food can be broken down
- carnivory and omnivory
Advantages of Gnathostome - other uses
- digging holes
- holding mates
What does natural selection often tinker with?
Preexisting structures
Where did the pharyngeal arch originate?
in filter feeders, but these arches have a number of anatomical components that can be tinkered with muscle, bone, nerves and blood vessels
How did pharyngeal arches occur?
- first 2 arches lost
- 3rd arch modified into upper and lower jaws
- 4th arch (hyoid arch) supports the jaw
- subsequent arch modified (usually) for respiration
What were the opportunities that jaws opened up?
- fish were no longer limited to prey that were smaller than their mouths
- the small ones could also protect themselves from larger fish
Jaws diversified quickly, largely at the expense of the jawless fishes
What are Chondrichthyes?
- cartilaginous fishes
- skeletal is cartilaginous
- bone restricted to teeth and scales
- in most groups notochord replaced by vertebral column
- unique scale type
- variable development
- fertilization always internal
- development can be oviparous, ovoviviparous or viviparous
Placoid scales?
Provide tough but aerodynamic skin
Clasper of the male
- an intermittent organ
- delivers sperm
- modified pelvic fins
Elasmobrnaches
- sharks, rays, skates
- usually 5 (sometimes 7)
uncovered gill slits - upper jaw hinged to
cranium
Holocephalians
- chimaeras or ratfishes
- gill slits hidden by
operculum - upper jaw fused to
cranium
Osteichthyes
- bony fish
- occur in all freshwater and marine habitats
- by far the most numerous of the vertebrates
- 96% of all fish
- range from 12 mm to 4.5mm
Ossification (Osteichthyes)
Internal skeleton, skull, operculum, fins, scales
Scales (Osteichthyes)
Most have some types of dermal scales
Air Sacs (Osteichthyes)
swim bladder (for
regulating bouyancy) or
lung (for respiration)
